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Newsletter

A very happy and peaceful Christmas, a lot of quality time with family and friends, and a Happy New Year - from editorial staff of the DIPOL Weekly Review.

"Engagingly about antennas" - Photo Contest 2008. First prize: HDTV DVB-S receiver. We invite everyone to take part in the 7th edition of the competition. Even though it is meant summer holiday project, we take into consideration pictures from all the seasons. So winter scenery can make for some really cool shots! And during your winter holiday you may also view the entries for the 2007 edition.

Works can be submitted from June 1st, 2008 to September 30, 2008. Rules of participation will be available soon.

Reception and amplification of FM broadcasts. In outlaying areas, far away from radio stations, there are problems with reception of signals from low-power FM transmitters. Another problem is caused by two orthogonal polarizations that are used. In cities, when the distances are usually short, a good solution is application of antennas receiving both polarizations - H and V - A0222, or A0223 (anodized). In the case of longer distances omnidirectional antennas are not recommended. Much better results are obtained by using two orthogonally oriented directional Yagi antennas. The antennas can be connected via e.g. ST 1-60 C0910 combiner. Weaker signals (mainly those of vertical polarization) can be additionally amplified, e.g. by the amplifier AP-FM B9013.Notice! Application of FM amplifier in the place where even one FM signal is strong (and the installation combines FM and TV signals) can result in overdriving active elements of the installation or receiving equipment - distortion products will be visible as interferences in televisions.

Compact cameras. They are equipped with IR illuminators, and usually prepared for outdoor operation, but first of all - the cameras are cheap and easy to install. Compact cameras are perfect for monitoring homes, houses, shops, small businesses.

Online viewing of four channels from video server Pixord P4504 K2132 (MPEG-4). There is now available source code for posting on a www site images from 4-channel video server P4504 K2132. It is enough to modify the utility by entering IP address of IP camera in the appropriate section of html code. An important advantage of the server is use of MPEG-4 compression, which reduces the video data stream in comparison with majority of digital video recorders employing MJPEG compression. It allows to provide access to the images for a greater number of visitors. The video server is the next device capable of uploading live video stream to a website, similarly to the cameras P400 K1131, P400W K1132, P405 K1133, P405W K1134 and the K2131 video server.

Pixord P4504 - 4-channel MJPEG/MPEG-4 video server with HDD option

How to upgrade and expand existing CCTV systems. Video servers easily allow to expand analog installations and simultaneously make the basis for digital IP system. As shown in the diagram below, adding the ACTi K2114 servers we don't change the existing infrastructure, but upgrade the whole system to modern IP network. The installation can be further developed without exchanging the original equipment, by employing new IP cameras , e.g. K1214, and if needed, by organizing monitoring centers based on Alnet K3208 software. This way any analog system based on DVR can be updated to state-of-the-art technology. (MW)

Expansion of CCTV system

Cameras with Wide Dynamic Range (WDR) sensor. WDR cameras use the newest generation of sensors from the American company Pixim. Every pixel of the sensor is an independent analog to digital converter. So every element has individually set exposition time, depending on light intensity. It eliminates under- and over-exposed areas in the image. This kind of cameras is perfect for viewing against the light. Standard cameras do not allow to view details in dark areas when other fragments of the image are very bright. Such situations are unavoidable when we monitor gateways flanked by bright neon signs, sidewalks under the glittering shop windows etc. They simply average out the video level, loosing details both in the brightest and darkest areas of the image. Using a WDR camera we can identify people who are in the darker part of the image, thanks to that feature of individual adjustment of the cells. The camera SN-586C/B WDR M11208 equipped with mechanically switching IR filter can be also used for indoor applications, where it should operate against the light, or the changes of light intensity are very large, e.g. on the stage in theaters etc. The device has very useful NightVision function that switches it into B/W mode when the light goes down.

How does DDNS work? Users of ADSL service (e.g. Neostrada in Poland) do not have a static IP - it is changed periodically. With this type of connectivity it is not possible to run a server, because the current IP address is unknown. The solution is provided by DDNS service. Similarly to DNS server, it provides a database containing relations between domain and numeric addresses, but this database may be updated on request by the domain owner. Thanks to this solution, the server is available in the domain address regardless its current IP number. In such a case, the access to the server is limited to its domain name translated by DDNS server. We have to remember that when DHCP server changes the IP, it takes some time to detect this change by the client software or router, and, after the notification is sent to DDNS server, it takes another minute or so to send this piece of data to DNS server and update the entry in the database. In result, our server will be periodically unavailable up to several minutes, every time the IP address has been changed.

Wireless connection of computers to the Internet. Some access points have several modes of operation. They can operate in WDS, Bridge (Point-to-Point), or multi-Bridge (Point-to-MultiPoint) modes. An example is the device WA-2204C N2647. In this case one AP (that operating in AP WDS mode) can cooperate with wireless client stations, whereas the second one (operating in Point-to-Point mode) is connected only with the AP-WDS.